Modularize to allow imports of parts of the system

The program has been modified to be organized into packages that can be exported without cloning the entire system. Now, using go get github.com/faithcomesbyhearing/fcbh-dataset-io/{package-name} one can obtains parts of the system.

In order that a client application could be developed, the package that produces the "compare" audio proofing report has been reorganized so that the data preparation is separated from the report itself. This will make it easy to develop other reports from the same data.